CO2 capture, activation and dissociation on the Ti2C surface and Ti2C MXene: the role of surface structure

Abstract

Atmospheric CO₂ is one of the main components of the greenhouse effect. To overcome this problem there are ongoing efforts to convert CO₂ to some other useful and harmless products. The capture, activation and dissociation of CO₂ are the preliminary steps in this process. In an effort to understand the role of surface composition and structure in CO₂ adsorption and dissociation, in this work, with the help of first principles density functional theory based calculations, we have studied the same on the {100} surface of cubic Ti₂C and MXene (also the {0001} surface of trigonal Ti₂C). Our results show that CO₂ undergoes barrierless chemisorption on both of these surfaces with a preference towards {100} cubic Ti₂C. We attribute the reason for this to a lower value of the work function of the {100} surface. Furthermore, on MXene, the barrier for CO₂ dissociation is lower compared to that on the {100} surface. Coverage dependent CO₂ chemisorption studies on these two surfaces show that on the Ti₂C surface the CO₂ molecules form clusters around the C-vacancies while on MXene they are uniformly spread on the surface.